Sealant for prevention of blowout, tubeless tire, and tire tube

ABSTRACT

The viscosity of a puncture-preventing sealant ( 7 ) is set in a range of 25 to 35 dPa·s, and a thixotropy index is set in a range of 6.5 to 11.0, the sealant ( 7 ) being filled in a sealant chamber ( 6 ) defined to extend along an outer periphery of an air chamber ( 5 ) in a tire (T). When the tire (T) is being rotated by traveling of a vehicle, the viscosity of the sealant ( 7 ) is reduced by a stirring action provided by a vibration or a centrifugal force of the sealant ( 7 ), whereby the sealant ( 7 ) can be diffused uniformly in the sealant chamber ( 6 ). When the vehicle has been stopped and the stirring action has been extinguished, the viscosity of the sealant ( 7 ) is increased, whereby the sealant ( 7 ) is maintained in a state in which it has been diffused uniformly in the sealant chamber ( 6 ) without flowing downwards in the sealant chamber ( 6 ) by gravitation. Therefore, even when the vehicle is travelling at a high speed, the generation of a vibration and a noise can be prevented. In this manner, the puncture-preventing sealant is provided, which has such a nature that the sealant is easy to flow due to a low viscosity during traveling of a vehicle, and the sealant is difficult to flow due to a high viscosity when the sealant is left to stand.

FIELD OF THE INVENTION

The present invention relates to a puncture-preventing sealant which isfilled in a sealant chamber defined to extend along an outer peripheryof an air chamber in a tire, as well as to a tubeless tire and a tiretube using such puncture-preventing sealant.

BACKGROUND ART

A tire using such a puncture-preventing sealant is already known fromJapanese Patent Application Laid-open No. 10-71806, for example. Theknown puncture-preventing sealant has a viscosity set in a range of 20to 23 dPa·s, and a thixotropy index set in a range of 5.5 to 5.8.

When a vehicle provided with a tire assembly comprising a tire using theabove known puncture-preventing sealant and assembled to a wheel istraveling at a high speed exceeding 100 km/hr, for example, a vibrationand/or a noise may be produced due to an unbalance of the tire assemblyin some cases. Such unbalance can be overcome by the correction using abalance weight. However, when the viscosity of the sealant is low, thefollowing problem is encountered: If the vehicle is left in a stoppedstate, the sealant flows to a lower portion of the sealant chamber bygravitation, whereby the tire assembly is brought again into itsunbalanced state. Another problem is that even if a static balance isprovided in a tire assembly comprising a tire assembled to a wheel, ascommonly conducted, the sealant is moved within the sealant chamber oncethe vehicle travels, resulting in the balance loss again. If theviscosity of the sealant is merely increased, the following problem isencountered: It is difficult to diffuse the sealant uniformly within thesealant chamber due to the rotation of the tire caused by traveling ofthe vehicle, and an appropriate sealability is not provided.

Therefore, the development of a sealant has been desired, which ispermitted to flow within the sealant chamber to become diffuseduniformly in a traveling state of a vehicle, and is difficult to flowwithin the sealant chamber in a left state, whereby the balance can beprevented from being lost.

DISCLOSURE OF THE INVENTION

The present invention has been accomplished in view of the circumstancesdescribed above, and it is an object of the present invention to ensurethat the puncture-preventing sealant has such a nature that the sealantis easy to flow due to a low viscosity during traveling of a vehicle,and is difficult to flow due to a high viscosity when it is left tostand, while ensuring that the puncture-preventing sealant has asealability equivalent to that of the known sealant, whereby thebalanceability can be enhanced.

To achieve the above object, according to a first aspect and feature ofthe present invention, there is proposed a puncture-preventing sealantwhich is filled in a sealant chamber defined to extend along an outerperiphery of an air chamber in a tire, the sealant having a viscosity ina range of 25 to 35 dPa·s, and a thixotropy index in a range of 6.5 to11.0.

With the above feature, the viscosity of the puncture-preventing sealantis in the range of 25 to 35 dPa·s, and the thixotropy index of thesealant is in the range of 6.5 to 11.0. Therefore, when the tire isbeing rotated by traveling of a vehicle, the viscosity of the sealant isreduced by a stirring action caused by a vibration or a centrifugalforce, whereby the sealant can be diffused uniformly within the sealantchamber. When the vehicle has been stopped, resulting in the eliminationof stirring action, the viscosity of the sealant is increased, wherebythe sealant is maintained in a state in which it has been diffuseduniformly without flowing downwards within the sealant chamber bygravitation. Therefore, a balanced state can be maintained, and evenwhen the vehicle travels at a high speed after lapse of a long time inthe stopped state of the vehicle, the generation of a vibration and anoise can be prevented.

Further, there is proposed a tubeless tire using a puncture-preventingsealant described above, the sealant chamber having a radial thicknessin a range of 1.2±0.3 mm.

With th above feature, the radial thickness of the sealant chamber isset in the range of 1.2±0.3 mm. Therefore, it is possible to prevent thethickness from being too large, causing the sealant to flow downwardsunder the action of the force of gravity, resulting in the balance loss,when the tire is left to stand, and to prevent the thickness from beingtoo small, causing the sealability for a puncture to be reduced, or toprevent the sealant from being difficult to diffuse uniformly within thesealant chamber. Thus, both of the balanceability and the sealability ofthe tire can be reconciled to the maximum.

Further, there is proposed a tire tube using a puncture-preventingsealant described above, the sealant chamber having a radial thicknessin a range of 1.2±0.3 mm.

With the above feature, the radial thickness of the sealant chamber isin the range of 1.2±0.3 mm. Therefore, it is possible to prevent thethickness from being too large, causing the sealant to flow downwards bygravitation, resulting in the balance loss, when the tire is left tostand, and to prevent the thickness from being too small, causing thesealability for a puncture to be reduced, or to prevent the sealant frombeing difficult to diffuse uniformly within the sealant chamber. Thus,both of the balanceability and the sealability of the tire can bereconciled to the maximum.

The above and other objects, features and advantages of the inventionwill become apparent from the following description of the preferredembodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 3 show embodiments of the present invention, wherein FIG. 1is a cross-sectional view of a wheel having a tubeless tire mountedthereon; FIG. 2 is a cross-sectional view of a wheel having atube-incorporated tire mounted thereon; and FIG. 3 is a graph showing acharacteristic of variation in viscosity with respect to the number ofdays on which a sealant has been left to stand.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will now be described by way of embodiments withreference to the accompanying drawings.

FIG. 1 shows an embodiment in which a sealant according to the presentinvention is utilized in a tubeless tire T. The tubeless tire T ismounted on a rim R of a wheel, and comprises a tire body 1 and an innerliner 2L adhered by vulcanization to the inside of the tire body 1. Theinner liner 2L includes a peripheral wall 3, which is formed into aU-shape in section and has air-chamber peripheral wall portions 3 i, 3 ilocated on the radially inner side of the tire T, and a sealant-chamberperipheral wall portion 3 o located on the radially outer side of thetire T. Connections between the air-chamber peripheral wall portions 3i, 3 i and the sealant-chamber peripheral wall portion 3 o of theperipheral wall 3 are connected to each other by a partition wall 4formed integrally with the peripheral wall 3. Air is filled in an airchamber 5 substantially circular in section and defined between theair-chamber peripheral wall portions 3 i, 3 i and the partition wall 4,and a gelled sealant 7 is filled in a sealant chamber 6 substantiallyarcuate in section and defined between the sealant-chamber peripheralwall portion 3 o and the partition wall 4.

The rim R includes an annular rim body 11 extending circumferentially ofthe tire T, and a pair of flange portions 12, 12 extending radiallyoutwards from widthwise opposite ends of the rim body 11 to retain aninner periphery of the tire body 1. A pneumatic valve 13 for filling airinto the air chamber 5 defined inside the inner liner 2L is supported toextend through a pneumatic valve-mounting portion 14 formed atcircumferentially one point on the rim body 11.

FIG. 2 shows an embodiment in which a sealant 7 according to the presentinvention is utilized in a tube-incorporated tire T. Thetube-incorporated tire T includes a tire tube 2T corresponding to theinner liner 2L of the above-described tubeless tire T. The tire tube 2Tis capable of being mounted and removed on and from the tire body 1, andincludes air-chamber peripheral wall portions 3 i, a sealant-chamberperipheral wall portion 3 o and a partition wall 4, as does the innerliner 2L. An air chamber 5 is defined between the air-chamber peripheralwall portions 3 i and the partition wall 4, so that air is filled in theair chamber 5, and a sealant chamber 6 is defined between thesealant-chamber peripheral wall portion 3 o and the partition wall 4, sothat a sealant 7 is filled in the sealant chamber 6. A pneumatic valve13 is mounted in the air-chamber peripheral wall portions 3 i of thetire tube 2T and supported to extend through a pneumatic valve-mountingportion 14 formed at circumferentially one point on the rim body 11.

Thus, the sealant chamber 6 in the inner liner 2L or the tire tube 2T ismaintained in a shape extending along the inside of a tread 15 by an airpressure in the air chamber 5. Therefore, even if the tire body 1 ispunctured radially or sideways by a nail or the like, the sealant 7fills the puncture immediately to repair it, thereby retarding theleakage of the air from the air chamber 5. The sealant 7 is retained inthe sealant chamber 6 and cannot flow out of the sealant chamber 6 intothe air chamber 5, and hence, the pneumatic valve 13, a pressure gaugeapplied to the pneumatic valve 13 and the like cannot be clogged.

The sealant 7 filled in the sealant chamber 6 will be described below.

When the tire T is being rotated by traveling of a vehicle, theviscosity of the sealant 7 in the present embodiment is reduced by astirring action provided by a vibration transmitted from a road surfaceor by a centrifugal force of the sealant 7, whereby the sealant 7 can bediffused uniformly in the annular sealant chamber 6 to provide a staticbalance and a dynamic balance for wheels. When the vehicle has beenstopped and left in a state in which the stirring action has beenextinguished, the viscosity of the sealant 7 is increased, whereby thesealant 7 is maintained in a state in which it has been diffuseduniformly in the sealant chamber 6 without flowing downwards in thesealant chamber 6 by gravitation. Therefore, when the vehicle istraveling at a high speed, the same state as in the balancing can bereproduced.

TABLE 1 Constituent % By weight Water 65 Propylene glycol 30 Thickener2.0 Nylon fiber 0.5 Cotton fiber 1.4 Ceramic powder 0.5 Dye 0.1

As shown in Table 1, constituents of the sealant 7 in the presentembodiment are 65% by weight of water, 30% by weight of propyleneglycol, 2.0% by weight of a thickener, 0.5% by weight of a nylon fiber,1.4% by weight of a cotton fiber, 0.5% by weight of a ceramic powder,and 0.1% by weight of a dye.

TABLE 2 Prior art Embodiment Viscosity 23 30 Thixotropy index 5.8 7.02Balanceability X ◯ Sealability for Δ-◯ ◯ puncture

As shown in Table 2, the prior art sealant has a viscosity of 23 dPa·sand a thixotropy index of 5.8, while the sealant 7 in the presentembodiment has a viscosity of 30 dPa·s and a thixotropy index of 7.02.The thixotropy index is a value determined according to JIS K5400, andthe viscosity is a value measured by a VT-04 type viscometer made byRION. The sealant 7 in the present embodiment has the thixotropy indexlarger than that of the prior art sealant and hence, shows a remarkedtendency to reduce in viscosity during traveling of the vehicle and toincrease in viscosity when the sealant is being left to stand. Thepuncture sealability of the sealant 7 in the present embodiment is alsosuperior to that of the prior art sealant due to the constituent of thesealant 7 shown in Table 1.

As shown in a graph in FIG. 3, in a tire using the prior art sealanthaving the lower thixotropy index, the unbalance amount is varied withan increase in number of days on which the sealant has been left tostand after traveling of the vehicle, but in the tire T using thesealant 7 in the present embodiment having the higher thixotropy index,the unbalance amount is maintained stably, even if the number of days onwhich the sealant has been left to stand after traveling of the vehicleis increased.

In the tire T in each of the embodiments shown in FIGS. 1 and 2, thesealant chamber 6 has a radial thickness t set in a range of 1.2±0.3 mmand thus, it is possible to exhibit the balanceability and the puncturesealability of the tire T to the maximum.

Although the embodiments of the present invention have been described indetail, it will be understood that the present invention is not limitedto the above-described embodiments, and various modifications in designmay be made without departing from the spirit and scope of the inventiondefined in claims.

For example, in the embodiments, the viscosity of the sealant 7 is 30dPa·s, and the thixotropy index is 7.02, but if the viscosity is set ina range of 25 to 35 dPa·s, and the thixotropy index is in a range of 6.5to 11.0, a desired effect can be provided.

1. A puncture-preventing sealant comprising 65% by weight of water, 30%by weight of propylene glycol, 2.0% by weight of a thickener, 0.5% byweight of a nylon fiber, 1.4% by weight of a cotton fiber, 0.5% byweight of a ceramic powder, and 0.1% by weight of a dye.
 2. A tubelesstire comprising a puncture-preventing sealant according to claim 1filled in a sealant chamber defined to extend along an outer peripheryof an air chamber in the tire, wherein said sealant chamber has a radialthickness in a range of 1.2±0.3 mm.
 3. A tire tube comprising apuncture-preventing sealant according to claim 1 filled in a sealantchamber defined to extend along an outer periphery of an air chamber inthe tire tube, said sealant chamber having a radial thickness in a rangeof 1.2±0.3 mm.